Paneles Fotovoltaicos

Renewable Energy 164 (2021) 867e875
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Renewable Energy
journal homepage: www.elsevier.com/locate/renene
An efficient pulsed- spray water cooling system for photovoltaic
panels: Experimental study and cost analysis
Amirhosein Hadipour a, Mehran Rajabi Zargarabadi a, *, Saman Rashidi b
a
b
Faculty of Mechanical Engineering, Semnan University, P.O.B. 35131-191, Semnan, Iran
Department of Energy, Faculty of New Science and Technologies, Semnan University, Semnan, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 13 February 2020
Received in revised form
18 August 2020
Accepted 3 September 2020
Available online 16 September 2020
Cooling of photovoltaic panels is an important factor in enhancing electrical efficiency, reducing solar cell
destruction, and maximizing the lifetime of these useful solar systems. Generally, the traditional cooling
techniques consume considerable amount of water, which can be a major problem for large scale
photovoltaic power stations. In this experimental study, a pulsed-spray water cooling system is designed
for photovoltaic panels to improve the efficiency of these solar systems and decrease the water consumption during the cooling process. The results of the photovoltaic panel with the pulsed-spray water
cooling system are compared with the steady-spray water cooling system and the uncooled photovoltaic
panel. A cost analysis is also conducted to determine the financial benefits of employing the new cooling
systems for the photovoltaic panels. The results show that as compared with the case of non-cooled
panel, the maximum electrical power output of the photovoltaic panel increases about 33.3%, 27.7%,
and 25.9% by using the steady-spray water cooling, the pulsed-spray water cooling with DC ¼ 1 and 0.2,
respectively. The pulsed-spray water cooling system with DC ¼ 0.2 can reduce the water consumption to
one-ninth in comparison with the case of steady-flow one. The levelized cost of electricity by the uncooled system was found lower than the spray-cooled systems but very near to pulsed-spray water
cooling with DC ¼ 0.2. The levelized cost of electricity produced by the PV system is reduced about 46.5%
and 76.3% by using the pulsed-spray water cooling system with DC ¼ 1 and 0.2, respectively as compared
with the case of steady-spray water cooling system. As a result, the new pulsed-spray water cooling is
efficient from the economic point of view.
© 2020 Elsevier Ltd. All rights reserved.
Keywords:
Photovoltaic panels
Water cooling system
Pulsed-spray
Electrical efficiency
Cost analysis
1. Introduction
Due to the increasing demand for energy and the limitation of
fossil energy sources as well as increasing environmental pollution,
the need to use renewable energy sources is very high. Photovoltaic
panels (PV) are the technology of the direct conversion of solar
energy into electrical energy. However, the energy conversion efficiency of these panels is quite low because most of solar energy is
lost as heat. Accordingly, the temperature of PV cells increases and
this leads to reduce the voltage and the electrical efficiency of the
system [1e3]. As a result, designing efficient cooling system for PV
panels is essential. Many studies have focused on the negative effects of increase in the temperature on the efficiency reduction of
PV panels. These investigations have shown that the electrical
* Corresponding author.
E-mail address: [email protected] (M. Rajabi Zargarabadi).
https://doi.org/10.1016/j.renene.2020.09.021
0960-1481/© 2020 Elsevier Ltd. All rights reserved.
efficiency can decrease about 0.5% with 1 C increase in panel
temperature [4,5].
In most of cooling methods designed for PV panels, water and
air are used as the working fluids. Air cooling needs less energy as
compared with water cooling, while, cooling capacity of water is
more than the cooling capacity of air. Wang et al. [6] focused on the
direct-contact fluid film cooling method used for the solar panel.
They controlled the mean temperature of the solar panel below
80 C by using this method. Jakhar et al. [7] used the water as the
coolant in the PV panel. They set the water channels at the rear of a
PV panel. Their results showed that this system can increase the
efficiency of the PV panel. Chandrasekar and Senthilkumar [8]
cooled down the PV panels by the heat spreaders in conjunction
with the cotton wick structures. They found that the temperature of
the PV panel decreases up to 12%, and the electrical efficiency of
this device increases about 14% by using this cooling technique.
Bahaidarah [9] investigated the potentials of jet impingement
cooling system for controlling the temperature of the PV panel.
A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi
Renewable Energy 164 (2021) 867e875
DC
CRF
O&M
i
n
LCOE
Pe
Nomenclature
Ap
a
e
E
P
r
Pe
h
Qe
Qc
Qr
Q loss
effective surface of the PV panel, (m2)
absorptivity
evaporation coefficient, (kg m2/s)
solar irradiation, W/m2
partial pressure, Pa
latent heat of the water evaporation, (J/kg)
electric power output of the PV panel, W
convection heat transfer coefficient, (W/m2 K)
total evaporation heat loss from the PV panel, (W)
total convection heat loss from the PV panel, (W)
total irradiation heat loss from the PV panel, (W)
overall heat loss from the PV panel, (W)
duty cycle (the ratio of on-time to off-time in a cycle)
capital recovery factor
operating and maintenance
Interest rate (%)
life of panel (years)
levelized cost of electricity
electric power output of the PV panel, W
Greek symbols
the uncertainty of different parameters
time period, (s)
StefaneBoltzmann constant, (W/m2 K4)
ε
emissivity
u
t
s
They recorded the maximum cell temperature of 69.7 C for an
uncooled panel. The jet impingement cooling system can decrease
the cell temperature about 31.1 C and 36.6 C for December and
June, respectively. In addition, the power efficiency improves up to
49.6% and 51.6% for December and June, respectively by using this
technique. Castanheira et al. [10] used the On/Off system instead of
continuous water flow in the PV power plant. It was concluded that
the annual energy production can be improved about 12% on a
5 kW section of a 20 kW plant by using this technique. In another
investigation, Fakouriyan et al. [11] designed a new cooling module
for the PV panel. They employed the hot water generated by
absorbing the thermal energy from the PV panel for supplying the
hot water for the domestic applications. They recorded the payback
period of 1.7 years for their system. Ni
zeti
c et al. [12] investigated
the performance and economic effects of the active cooling modules for the PV panel. They found that 10%e20% improvement in the
performance can be achieved by using the water cooling techniques. In addition, their economic study indicated that the active
cooling techniques are not economically viable and they need the
advanced control systems to reduce their costs. Generally, in the
water cooling systems, the water is sprinkled on the surface of PV
panel or the water channels are used to control the temperature of
the panel [13e16]. Yang et al. [17] integrated a spray cooling
module with a shallow geothermal energy heat exchanger to
improve the efficiency of the PV panels. They concluded that the
system with a u-shaped borehole heat exchanger is more efficient
than the system without the u-shaped borehole heat exchanger.
Bahaidarah et al. [18] reviewed the PV panel cooling systems. Their
review showed that the active cooling by impingement jet,
microchannels, and hybrid impingement jet-microchannel are
more effective for removing high heat flux from the PV surfaces.
Abdolzadeh and Ameri [19] sprayed the water on the front side of
the PV panel. They observed the significant improvement in the
electrical efficiency of the system by using this technique. In an
experimental study, Ni
zeti
c et al. [20] investigated the effect of
water spray cooling on the PV panel performance. They investigated the effects of the water spray cooling system on the performance of PV panel for three cases. They used the water spray on the
front side, back side, and both back and front sides of the PV panel
in these cases. Their results showed that for the case of the water
spray used on the front side, the efficiency of PV panel is significantly better than the case of the water spray employed on the back
side. A back side water cooling method is used by Bahaidarah et al.
[21]. Their results showed that the electrical efficiency can be
improved about 9% for the hot climate condition by using this
cooling method. Rahimi et al. [22] performed both experimental
and numerical investigations on a jet impingement cooling system
used to improve the efficiency of the PV panel in a hybrid wind and
solar system. They observed that the total power generated by the
system increases about 21% by using the jet impingement cooling
system as compared with the simple cooling system. There are
other studies about using water as the coolant for the PV panels
[23e25]. In all these studies, the power output was increased in the
range of 10%e20% by using the cooling techniques. In the experimental and numerical studies, Chow et al. [26] investigated the
effects of different parameters on the performance of a PV-thermal
system. They used the water as the working fluid. They showed that
the efficiency of PV-thermal system enhances by using the glass
cover. Tiwari et al. [27] examined the effects of ambient temperature on the efficiency of the PV panels. They conducted their experiments in the summer days. Their results showed that in the
midday, the PV system has the least efficiency as the air temperature is high. Alami [28] studied the effects of the evaporative
cooling implemented on the PV system. It was found that the power
output of the PV system can increase up to 19% by using this cooling
technique.
The literature review indicated that the efficiency of PV systems
can improve considerably by using an efficient cooling technique.
The previous studies conducted on the water spray cooling systems
showed that the cooling of PV panel from the front is significantly
better as compared with other cases [19,20]. In most cases, the
cooling system with the steady-flow design was used to cool down
and control the temperature of the PV panels in the previous
studies. However, these systems consume considerable amount of
water, which can be a major problem for large scale PV power
stations. As a result, in the present study, a pulsed-spray water
cooling system is designed and tested to cool down the PV panel
and decrease the water consumed during the cooling process. The
electrical efficiency of the PV panel, IeV characteristic curves,
temperature of cells, and the amount of water consumed during the
cooling process are investigated for two cooling systems. The results of the PV panel with the pulsed-flow spray cooling system are
compared with the steady-spray water cooling system and the
uncooled PV panel. Finally, a cost analysis is arranged to determine
the financial benefits of employing the new cooling systems for the
photovoltaic panels.
2. Experimental setup
2.1. Experimental procedure details
In this study, the experimental setup comprises of two PV units.
Each PV unit has 36 monocrystalline silicon solar cells. The details
of the units are presented in Table 1. The realistic and schematic
868
A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi
Renewable Energy 164 (2021) 867e875
illustrations of the experimental setup are shown in Figs. 1 and 2. As
shown in Fig. 1, one of the PV panels has a spray cooling system,
while the other one is not equipped with the cooling system. Two
systems are placed in the direction of the south with angle of 30
with respect to the horizontal. They are tested under the same
conditions. The cooling nozzles are also placed with angle of 30
with respect to the PV panel. The cooling system has 9 five-micron
nozzles with 12 cm distance with each other. The nozzle type is a
simple orifice and the distance between the nozzle and PV panel is
8 cm. In this experiment, a solenoid valve is used to regulate the
periodicity of the water spray (See Fig. 2). The infrared camera and
the type K thermocouple are employed to measure the temperatures of the PV cells and ambient, respectively. The current and
voltage are measured by using the digital multimeter with data
storage capability. In addition, the total solar radiation is measured
by a pyranometer with data storage capability. The pyranometer is
installed parallel to the PV panel. The experimental data are
collected on the certain days of June 2019 from 11:30 a.m. to 3:30
p.m., at 10-min intervals. The tests are carried out in Semnan with
geographical coordinates of 53 230 E, 35 330 N, Iran.
Fig. 1. Photograph of the PV panel.
2.2. Uncertainty analysis
The uncertainties of the measuring instruments used in the
experiment are presented in Table 2. To analyze the uncertainties of
measurements in the experiments, the equation of uncertainty and
the measurement error provided by Holman [29] are used. The
uncertainty for the efficiency of PV panel is defined by:
uh
¼
h
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
u 2 u 2 u 2 u 2
Ac
V
I
E
þ
þ
þ
V
I
E
Ac
(1)
where V, I, E, and Ac are the voltage, current, solar irradiation, and
cross-section of the PV panel, respectively. u indicatesthe uncertainty of different parameters and h is the efficiency of the PV panel.
The maximum uncertainty of the efficiency of the PV panel recorded in the experiment is 2.92%.
Fig. 2. Schematic view of the PV panel with spray cooling system.
3. Theoretical aspects and analytical model
Table 2
Uncertainties of measuring instruments.
As already mentioned, a row of water spray nozzles with periodical and steady flows is used as the cooling system in this study to
reduce the temperature of PV panel and increase the electric power
output of this solar system. Generally, a small portion of the solar
irradiation, E, received by the panel surface, Ap; can be used to
generate the electrical power. The major amount of the solar irradiation is used to increase the internal energy of PV panel as DUpanel
and the rest amount is wasted into the surroundings as Qloss .
General energy flows and heat transfer mechanisms in the PV panel
are disclosed in Fig. 3. As shown in this figure, the overall heat loss
consists of convection, QC , radiation, QR , and evaporation heat loss,
QE . The solar irradiation received by the PV panel, as the energy
input of the system, is defined by:
Measuring instrument
Uncertainty
Infrared camera
Pyranometer
Voltmeter
Amperemeter
±0.4
±5
±0.5
±0.5
QSolar ¼ a:E:Ap
(2)
where a is the absorption coefficient. The overall heat loss can be
calculated as follows:
Table 1
Details of the examined PV panel.
.
PV panel characteristics under the standard conditions (E ¼ 1000W
and T ¼ 25 C)
m2
Model
Number of cells in the module
Maximum power
Current at P max/short-circuit current
Voltage at P max/open-circuit current
Dimensions
Energy class
869
STP085B-12/BEA
36
85 W ± 5%
4.8/5.15 A
17.8/22.2 V
1195 mm*541 mm*30 mm
A
A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi
Renewable Energy 164 (2021) 867e875
the heat rejection from the panel surface, which is highly related to
the evaporation coefficient. In addition, the evaporation coefficient
depends on the surrounding air conditions and the average temperature of the water film on the panel surfaces.
4. Results and discussion
Fig. 4 shows the different flow modes considered for the cooling
system in this study. To obtain the reliable results, the PV panel is
tested in four different circumstances. These circumstances are
listed as follows:
(a) PV panel without the cooling system
(b) PV panel cooled down by the steady-flow water spray cooling system
(c) PV panel cooled down by the pulsed-spray water cooling
system with the duty cycle (DC) of 1. The duty cycle is defined
as the ratio of on-time to off-time in a cycle.
(d) PV panel cooled down by the pulsed-spray water cooling
system with the duty cycle of 0.2.
Fig. 3. General energy flows and heat transfer mechanisms from the PV panel.
Qloss ¼ QC þ QR þ QE
(3)
The heat lost by the convection should be considered for both
sides of the PV panel as follows:
QC ¼ QC;F þ QC;B
The water flow rates considered for the pulsed-spray cooling
systems with DC ¼ 0.2 and 1 are 0.12 and 0.52 L/min per m2 of PV
module, respectively. In addition, the water flow rate used for the
steady flow cooling system is 1.24 L/min per m2 of PV module.
(4)
where QC;F and QC;B are the heats lost by the convection from the
front and back sides of the PV panel, respectively. QC;F and Q C;B are
calculated by:
4.1. General experiment circumstances
QC;F ¼ hF Ap TP;F Ta;F
QC;B ¼ hB Ap TP;B Ta;B
The experimental data were obtained on the specific summer
days with ambient temperature in the range of 28 Ce31 C. All
experiments were performed outdoors with the air velocity in the
range of 1e1.4 m/s. The effect of air velocity changes on heat
transfer from the PV panel is negligible. The inlet water temperature is approximately constant at 18 C. Fig. 5 displays the intensity
of solar irradiation during the experiment for June 04, 2019. The
data in this figure are obtained at 10-min intervals. According to
this data, the average amount of solar irradiation is 985 W=m2 .
(5)
The overall heat lost by the radiation can be expressed as
follows:
QR ¼ QR;F þ QR;B
(6)
where QR;F and QR;B are the heats lost by the radiation from the
front and back sides of the PV panel, respectively. QR is defined by:
QR ¼ s:ε:Ap :Fxy Tx4 Ty4
4.2. The effect of pulsed-spray water cooling system on the
electrical power output and electrical efficiency of the PV panel
(7)
Fig. 6 shows the effect of different values of duty cycle on the
maximum electrical efficiency. As shown in this figure, by
decreasing DC to 0.16, 0.13, and 0.1, the maximum electrical efficiency significantly decreases, while, by decreasing DC to 1 and 0.2,
small changes in maximum electrical efficiency can be observed
In this equation, Fxy is the appropriate view factor for the front
and back sides of the PV panel.
The overall heat lost by the evaporation is related to different
parameters such as the temperature of water flow sprayed on the
PV panel, surrounding air temperature, surrounding air velocity,
and relative humidity of surrounding air. Since in this study a row of
water jet is sprayed on the front side of the PV panel, the heat lost
by the evaporation can be obtained by using the following
equation:
QE ¼ QE;F
(8)
The general form of the heat lost by the evaporation is:
QE ¼ e:Ap :ðPs Pd Þ:r
(9)
where e and r represent the evaporation factor and the latent heat
of evaporation, respectively. Ps and Pd are the partial pressures.
The evaporation coefficient has a significant influence on the
evaporation heat loss, which generally depends on the surrounding
air temperature, water jet temperature, and relative humidity of
the surrounding air. Due to the heat transfer rate between the panel
surface and the water jet, the average temperature of the panel is
also very important. The main purpose of this study is to increase
Fig. 4. Velocity profiles of water jet sprayed on the PV panel.
870
A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi
Renewable Energy 164 (2021) 867e875
efficiency of solar panels are mainly affected by the visible portion
of the solar spectrums rather than the infra-red light.
Fig. 8 illustrates the variations of the electrical power output
versus the voltage for four cases (cases a to b) in the period of
highest solar irradiation levels. As can be seen in this figure, the
maximum electrical power output is 54 W for the uncooled panel.
In addition, the maximum electrical power outputs of 72 W, 69 W,
and 68 W can be achieved by using steady cooling system, pulsed
cooling systems with DC ¼ 1, and DC ¼ 0.2, respectively in the PV
panel.
As a result, the maximum electrical power output of the PV
panel increases about 33.3%, 27.7%, and 25.9% by using steady
cooling system, pulsed cooling systems with DC ¼ 1, and DC ¼ 0.2,
respectively as compared with the case of uncooled panel. The
maximum electrical power output for the uncooled panel is
recorded at voltage of 13.5 V. For three PV panels with the cooling
system, this voltage is shifted to about 17 V. It is clear that the use of
a water spray cooling system causes to shift the point with the
maximum output power to a higher voltage.
Fig. 9 discloses the IeV characteristic curves for four cases. The
mean maximal electrical efficiency of 9.1% is recorded for the case
of uncooled PV panel. The efficiencies of 12.1%, 11.6%, and 11.5% can
be achieved by using steady cooling system, pulsed cooling systems
with DC ¼ 1, and DC ¼ 0.2, respectively. Accordingly, as compared
with the case of uncooled PV panel, the mean output power increases about 29.6%, 25.2%, and 24.1%, respectively as the steady
cooling system, pulsed cooling systems with DC ¼ 1, and DC ¼ 0.2
were applied. Generally, the short circuit current and open circuit
voltage are under the influence of the temperature variation of the
cells. The results of previous studies indicated that the open circuit
voltage reduces with increasing the temperature of cells. This leads
to decrease in the electrical efficiency of PV panel [30]. In addition,
the dusts can decrease the panel efficiency. Dusts act as a barrier
and prevent from the penetration of the sunlight through the PV
module glass cover and barricade to reach the solar cells. In this
situation, free electrons cannot be excited to conduction band by
the photons of sunlight radiation and hole-electron cannot be
separated. As a result, the electric currents cannot be generated by
the PV cells. This results in a considerable decrease in PV efficiency
[32]. These dusts can be removed by using the water spray cooling
system in the front of the panel. All three cooling systems considered in this study can decrease the temperature of PV panel and
remove the dusts from the panel surface.
As shown in Figs. 8 and 9, the differences between the electrical
power outputs of three cooling systems are negligible. However,
the pulsed-spray cooling system is more efficient as it consumes
lower amount of water. It should be highlighted that although the
water flow rate is reduced considerably by using a pulsed-spray
cooling system, but the panel remains moist. Accordingly, the
panel can be cooled down after disconnecting the water jet.
Fig. 5. Variation of solar irradiation intensity during the experiment for June 04, 2019.
Fig. 6. Effects of the periodic water jet flow on the electrical efficiency and the water
consumption.
between the steady cooling system and the pulsed-spray cooling
systems with DC ¼ 1 and 0.2. However, the water consumption is
drastically reduced.
The effects of the periodic water jet flow on the electrical efficiency and the water consumed by the cooling system for different
pulsations are shown in Fig. 6. It can be seen that the panels cooled
down by the pulsed-spray cooling systems with DC ¼ 1 and 0.2
have approximately the same values of the maximum electrical
efficiency. The panel cooled down by the pulsed-spray cooling
systems with DC ¼ 1 and 0.2 have approximately the same values of
the maximum electrical efficiency has only 5% lower maximum
electrical efficiency as compared with the panel cooled down by the
steady-flow cooling system. However, the pulsed-spray cooling
system with DC ¼ 0.2 can reduce the water consumption to oneninth in comparison with the case of the steady-flow cooling
system.
Fig. 7 shows the effects of cooling method on temperature and
power output of the PV panel for different intensities of solar
irradiation. According to this figure, the water spraying cooling is
more effective in high solar irradiation. It can be seen that as the
solar irradiation increases from 800 to 1200 W/m2, more temperature reduction is observed in PV panel and consequently, higher
power output can be achieved. It can be concluded that the increase
in solar irradiation from 800 to 1200 W/m2 does not affect the
priority of cooling method.
It should be noted that the reflection of electromagnetic radiations by water film in the PV panel with cooling system is small.
However, during the transmission of electromagnetic radiations
through the water layer, a portion of the electromagnetic spectrums may be absorbed by the water molecules. This absorption
occurs at a specified range of wavelengths. Fortunately, the absorption occurs mainly in the red-infrared region [31] and the
4.3. The effect of different cooling systems on the panel temperature
reduction
The variations of the temperature of PV cells with time for four
cases are shown in Fig. 10. It can be seen that the temperature of the
panel surface decreases considerably by using different cooling
systems. The temperature of panel surface for the uncooled PV
system is varied in the range of 56.8 C and 57.9 C, while by
applying the spray cooling systems, pulsed-flow or steady-flow, the
temperature of panel surface can be varied in the range of
24.2 Ce27.8 C. The results of previous studies showed that by
using a steady-spray cooling system, the temperature of panel
surface can decrease about 2.4 times in comparison with the case of
uncooled panel [19,20].
871
A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi
Renewable Energy 164 (2021) 867e875
Fig. 7. Effect of variations in solar irradiation on (a) PV temperature and (b) electrical efficiency.
Fig. 8. Variations of electrical power output with the voltage for four cases (cases a to
b).
Fig. 10. Effects of different cooling systems on the panel temperature reduction.
panel temperature decreases from 26.5 C to 57.1 C by using the
pulsed cooling system with DC ¼ 0.2 instead of the uncooled panel.
The results of this experimental study for different cases in the
highest solar irradiation levels are summarized in Table 3. The effects of periodic water jet flow on the electrical efficiency, electrical
power output, and temperature of PV panel surface are presented
in this table. As can be seen from the results, the steady-spray
cooling system has the best cooling mode, but there is no important difference between the electrical efficiencies for the cases of
the steady-flow and pulsed-spray cooling systems. As a result, it is
recommended to use the pulsed-spray cooling system for PV panels
as this system can reduce the water consumption significantly.
Fig. 9. IeV characteristic curves for four cases.
5. Cost analysis
A cost analysis is conducted for the proposed system. This analysis is important as it can determine the cost of electricity generated
by the PV system [33e35]. The details of cost analysis are presented
in the appendix. The results of this analysis for four cases are presented in Table 4. The life of panel is ten years, n ¼ 10. It should be
pointed out that for the ideal environmental conditions and under
certain other conditions, the lifetime of PV panels may be about 30
years. However, the operating temperature has the considerable effects on degradation of PV panels. The lifetime of PV panels can
drastically decrease with increasing the operating temperature. For
example, Ogbomo et al. [36] presented a model to predict the lifetime of the PV panel under different operating conditions. Their
The same temperature reduction can be observed by using the
pulsed-spray cooling system. However, the water consumption
reduces considerably by using a pulsed-spray cooling system as
compared with the case of steady-spray cooling system.
The effects of different cooling systems on the mean electrical
efficiency and mean temperature of PV panel are investigated in
Fig. 11. This figure shows that the mean electrical efficiency and the
mean temperature of the panel cooled down by three cooling
systems, steady cooling system, pulsed cooling systems with
DC ¼ 1, and DC ¼ 0.2, are approximately the same. The panel
electrical efficiency increases from 9.1% to 11.5%, while the mean
872
A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi
Renewable Energy 164 (2021) 867e875
Fig. 11. Effects of different cooling systems on the mean electrical efficiency and mean
temperature of PV panel.
Fig. 12. Comparison between the costs and electrical efficiencies of all PV systems.
Table 3
Highlights of different cooling systems investigated in this paper.
Type of cooling system
Power output
(W)
Uncooled PV panel
54
Steady-cooling system
72
Pulsed-cooling system with DC ¼ 1 69
Pulsed-cooling system with
68
DC ¼ 0.2
Average temperature of panel
( C)
Increase in power output
(%)
Electrical efficiency
(%)
Water consumption (L/
min)
57.1
24.8
25.7
26.5
e
33.3
27.7
25.9
9.1
12.1
11.6
11.5
e
0.81
0.32
0.078
Table 4
The results of the cost analysis for four cases and n ¼ 10.
Type of PV system
i (Interest rate (%)) CRF
Capital cost
($)a
O&M
($)
Water cost
($)b
Cooling system cost
($)c
Annual output
(kWh)
LCOE
($/kWh)
Uncooled PV panel
20 (10)
160
4.8
0
0
166.0
0.26 (0.20)
Steady-spray cooling system
20 (10)
160
4.8
311
8
220.8
1.61 (1.54)
160
4.8
131
40
211.7
0.86 (0.78)
160
4.8
29
40
209.8
0.38 (0.3)
Pulsed-spray cooling system DC ¼ 1 20 (10)
Pulsed-spray cooling system
DC ¼ 0.2
20 (10)
0.24
(0.15)
0.24
(0.15)
0.24
(0.15)
0.24
(0.15)
In this study, all costs of system are calculated based on the prices in Iran.
a
The capital cost includes all costs of the PV system, such as the costs of mounting frames, cables, inverters, etc.).
b
In this study, the cost of water is calculated based on the price of water in Iran (2.2 $/m3).
c
The cooling system cost includes the costs of jet nozzle assembly, solenoid value, and electricity consumed by the solenoid valve and piping. Also, in this study the city
water pressure is used.
cooling system with DC ¼ 0.2 has considerable higher efficiency
and the slight higher cost as compared with the case of uncooled PV
panel. As a result, this pulsed-spray cooling system is recommended for the usage in the practical applications.
The results of sensitivity analysis for various economic parameters are shown in Fig. 13. For the sample, a photovoltaic system
with pulsed cooling with DC ¼ 1 is considered and the costs of all
parameters, such as the water cost, cooling system costs, PV module
cost, etc. are reduced by 50% to determine the parameter with the
highest impact on LCOE. As shown in Fig. 13, the cost of water
consumption has the most impact on LCOE and the reduction in the
cost of water reduces the LCOE, significantly. In addition, the cost of
cooling system equipment has the least impact on the LCOE. As a
result, in this study, it is recommended to use the pulsed-spray
water cooling system as it can increase the electrical efficiency of
the PV system and reduce the water consumption and cost.
Accordingly, for countries with high water costs, it is recommended
to use a pulsed-spray water cooling system with the low-duty cycle
(DC) cooling system.
results showed that the lifetime of panel can be reduced to 9 years
for hot climate. The proposed cooling system can be widely used for
PV systems installed in the regions with hot climate. As a result,
n ¼ 10 years is selected for the lifetime of the system in this study. In
addition, the levelized costs of electricity produced by four PV systems are compared in Table 4. It can be seen that the levelized cost of
electricity produced by the PV system is reduced about 46.5% and
76.3% by using the pulsed-spray cooling systems with DC ¼ 1 and 0.2,
respectively as compared with the case of steady-spray cooling
system. As a result, the new pulsed-spray cooling system is efficient
from the economic point of view. It should be highlighted that the
use of cooling system can eliminate the hot spots on the panel surface and accordingly, increases the lifetime of the panel, which is also
benefit from the economic point of view.
The costs and electrical efficiencies of all PV systems are
compered in Fig. 12. As shown in this figure, the uncooled PV panel
has the minimum cost, while the panel with the steady-spray
cooling system has the maximum cost. However, the efficiency of
uncooled PV panel is significantly lower as compared with other
systems. The usage of steady-spray cooling system imposes
considerable cost on the system. The panel with the pulsed-spray
873
A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi
Renewable Energy 164 (2021) 867e875
draft, Formal analysis, Writing - review & editing, conceived of the
presented idea, developed the theory and performed the computations, carried out the experiment, wrote the manuscript, discussed the results and commented on the manuscript, processed
the experimental data, performed the analysis, drafted the manuscript and designed the figures, wrote Review & Editing. Mehran
Rajabi Zargarabadi: Conceptualization, Writing - original draft,
Formal analysis, Writing - review & editing, conceived of the presented idea, wrote the manuscript, discussed the results and
commented on the manuscript, processed the experimental data,
performed the analysis, drafted the manuscript and designed the
figures, wrote Review & Editing. Saman Rashidi: Writing - original
draft, Formal analysis, Writing - review & editing, developed the
theory and performed the computations, wrote the manuscript,
processed the experimental data, performed the analysis, drafted
the manuscript and designed the figures, wrote Review & Editing.
Fig. 13. Sensitivity analysis: Re-calculated LCOEs for the DC ¼ 1 pulsed-spray cooling
system if key financial and cost parameters are reduced by 50% (reference LCOE
$0.86 at 100%).
6. Conclusion
In the present experimental study, a pulsed-spray cooling system
was designed for the PV panels. The results of this design were
compared with the steady-spray cooling system and the case of
uncooled panel. The electrical efficiency of the PV panel, IeV characteristic curves, temperature of cells, and the water consumed
during the cooling process were investigated for two cooling systems. The main results of this study are summarized as follows:
Declaration of competing interest
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.
Appendix
The maximum electrical power output of the PV panel increases
about 33.3%, 27.7%, and 25.9% by using the steady-flow water
spray cooling system, pulsed-spray cooling system with DC ¼ 1,
and 0.2, respectively as compared with the case of uncooled
panel.
The electrical efficiency decreases from 12.1% to 11.5% by using
the panel cooled down by the pulsed-spray cooling system
instead of panel cooled down by the steady-flow cooling system.
However, the pulsed-spray cooling system with DC ¼ 0.2 can
reduce the water consumption to one-ninth in comparison with
the case of steady-flow cooling system.
The temperature of panel surface reduces from 57.1 C to 24.8 C
and 26.5 C by using the steady-spray cooling system and
pulsed-flow cooling system with DC ¼ 0.2, respectively as
compared to the uncooled PV system.
The levelized cost of electricity produced by the PV system is
reduced about 46.5% and 76.3% by using the pulsed-spray
cooling system with DC ¼ 1 and 0.2, respectively as compared
with the case of steady-spray cooling system.
The levelized cost of electricity by the uncooled system was
found lower than the spray-cooled systems but very near to
pulsed-spray water cooling with DC ¼ 0.2. It should be
mentioned that the small additional cost of the pulsed-cooling
system can be justifiable in cases where high ambient temperatures cause premature failures of uncooled PV modules.
The cost of PV system is expressed by cost per area ($/m2).
However, the modules are often sold based on their cost per peak
watt ($/Wp). Wp is potentially generated under peak solar irradiance
conditions. The following equation is used to convert the cost per
square meter to the cost per peak watt [33,37]:
$
Wp ¼
$=m2
h:1000Wp=m2
In this study, the peak solar irradiance is 1000 W/m2 and the
photovoltaic panel with cost of 160 $/m2 is used. Accordingly, the
cost per peak watt is 1.3 $/Wp for different modes investigated with
the efficiency of h ¼ 12%.
As the basic economic concept for each PV system, the costs
should be recovered by the useful energy produced by the system
over its lifetime. The levelized cost of electricity, LCOE, is defined as
the ratio of the total cost of life cycle to the total lifetime energy
production based on the following equation [33,37,39]:
LCOE ¼
ðAnuual cost þ O&MÞ ð$Þ
Anuual output cost ðkWhÞ
(A2)
The following equation is used to calculate the capital recovery
factor, CRF, for the PV systems [34,38]:
CRF ¼
CRediT authorship contribution statement
ið1 þ iÞn
ð1 þ iÞn 1
(A3)
The parameters, required to calculate the LCOE, are given in
Table A1 [34].
Amirhosein Hadipour: Conceptualization, Writing - original
Table A1
The parameters required to calculate the LCOE
Annual output ¼ Average Annual Insolation Efficiency
5KWh
365day
¼ 1825 kWh
day:m2
year
Annual Cost ¼ (Installation Cost CRF) þ water cost þ (cooling system cost CRF) þ O&M (O&M ¼ 3% of installation Cost per year)
Installation Cost ¼ Capital Cost Station Capacity ¼ 160$
Station Capacity ¼ 1 m2
a
Capital Cost ¼ 160 $/m2 or (1.3 $/W)
Average Annual Insolation ¼
a
(A1)
The capital cost includes all costs of the PV system (mounting frames, cables, inverters, etc.).
874
A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi
Renewable Energy 164 (2021) 867e875
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